Add redshift

> Redshift adjusts the color temperature of your screen according to
your surroundings. This may help your eyes hurt less if you are working
in front of the screen at night.

https://github.com/jonls/redshift
https://nixos.wiki/wiki/Redshift

nix/hosts/t490/configuration.nix

@@ -19,6 +19,7 @@
     autorandr.enable = true;
     dwm.enable = true;
     gaming.enable = true;
+    redshift.enable = true;
     st.enable = true;
     thunar.enable = true;
     peek.enable = true;

nix/hosts/t490/services/default.nix

@@ -2,6 +2,7 @@
   imports = [
     ./cron.nix
     ./interception-tools.nix
+    ./redshift.nix
     ./sound.nix
     ./udev.nix
     ./xserver.nix

nix/hosts/t490/services/redshift.nix

@@ -0,0 +1,31 @@
+{ config, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.nixosModules.redshift;
+in
+{
+  options.nixosModules.redshift.enable = mkEnableOption "Enable redshift";
+
+  config = mkIf cfg.enable {
+    location = {
+      latitude = 51.48;
+      longitude = -3.17;
+    };
+
+    services.redshift = {
+      enable = true;
+
+      brightness = {
+        day = "1";
+        night = "1";
+      };
+
+      temperature = {
+        day = 5500;
+        night = 3700;
+      };
+    };
+  };
+}